Social Media Technology for Treating Tobacco Addiction. The internet was built for communication. This research project, with its cutting-edge social network approaches and analyses, will examine the potential of the internet, and more specifically social media, to engage health communications for quitting smoking and preventing relapse for addiction treatment and cancer prevention. Further, the design tests the personalized benefits and treatment processes of a women-centered internet cessation intervention. With initial funding from an NIH R34 innovation award, we developed and evaluated a novel online social media intervention for tobacco cessation called Tweet2Quit. Tweet2Quit is a 100-day online intervention that uses a novel, low cost, automated approach to encourage and direct peer-to-peer social support for quitting smoking. Private Twitter groups of 24 smokers are set up, and engagement is encouraged and directed by daily auto feedback and daily auto messages that suggest discussion topics consistent with US treatment guidelines for tobacco use cessation. In a randomized controlled trial (N=160), all participants received advice to quit, referral to the NCI Smokefree.gov website, and 8 weeks of nicotine patch (usual care); and half were then randomized to a Tweet2Quit peer support group to test the net benefit of the social media intervention. At 60-days follow- up, Tweet2Quit participants reported 40% sustained abstinence compared to 20% for controls (p=.017), and engagement in the intervention was related to abstinence (p<.001). Consistent with the tobacco treatment literature, in both study conditions, men were more likely to quit smoking than women, and the gender effect in Tweet2Quit was moderate (d=.55). Notably, women in Tweet2Quit tweeted as much as the men, though the content differed thematically. The proposed randomized controlled evaluation (N=960) of the Tweet2Quit intervention will biochemically verify abstinence out to 6-months follow-up and will test the personalized benefit for women of a women-only versus co-ed Tweet2Quit group. In a 3-arm design, we will compare: 1) usual care, 2) Tweet2Quit-coed, and 3) Tweet2Quit-women only. Each 24-person Tweet2Quit group will include 12 buddy pairs based on similarity in demographics and abstinence goals. Also automated pattern detection will identify dips in tweeting and trigger automated alerts and engagement strategies. Our primary aims test hypothesis 1: Relative to usual care (n=240), Tweet2Quit-coed groups (n=480) will achieve significantly greater bioconfirmed sustained abstinence out to 6-months follow-up, and hypothesis 2: Women in Tweet2Quit will achieve significantly greater bioconfirmed 6-months abstinence in woman-only groups (n=240) vs. coed groups (n=240 women). Our secondary aims are to test the same hypotheses based on 3-month (end of treatment) sustained abstinence and 7-day point prevalence at 1, 3, and 6 months. Exploratory aims will study the Tweet2Quit groups' social network structures with a focus on the identification of buddy pairs and social brokers and test if these relationships are stronger for women in women-only groups versus women in coed groups of Tweet2Quit.